analysis of light single- hypernuclei events in nuclear emulsion detected with overall-scanning...

1

Analysis of Light Single-L Hypernuclei Events in Nuclear Emulsion Detected with Overall-scanning Method

MYINT KYAW SOE, Kazuma NAKAZAWA, Kaoru HOSHINO, Hiroki ITO, Kazunori ITONAGA, Hidetaka KOBAYASHI, Yoko ENDO ,

Junya YOSHIDA, Khin T. TINT, Shinji KINBARA, Akihiro MISHINA

Introduction Review experiments for Life-

time of L3H

Outline

30/11/2014

Nuclear Emulsion

Searching 3LH hypernucleus

events in nuclear emulsion

Gifu UniversityJapan

Estimation of mesonic decay events Summary

Introduction

2

L3H is the most basic and simple hypernuclear bound system among hypernuclei

n

L

pBL= 0.13 ±0.05 MeV

So far its life-time estimated by any experiments has large interval in each other

Life-time for L3H are estimated by experiments

In order to provide precise information of life-time and BL with small

error for L3H

high statistics events for L3H are requiered

Less than and nearly 180 ps

Aim is to measure the life-time and BL of light single- L hypernuclei with nuclear emulsion experiment

3

Review experiments for Life-time of L3H

1) Counter experiments

HypHI collaboration [1] 6Li+12C at 2A GeV

Observed the life-time for L3H : 183+42

-32 ± 37 ps & for :L 262+56-43 ± 45ps

STAR at BNL RHIC [2]197Au+197Au

Observed lifetime for 3LH, 138+26-22 ps

Above two counter experiments inform the life-time of 3LH is shorter than that of free L and their estimation

interval is large

[1] C.Rappold et al. Nuclear Physics A913 (2013) 170-184

http://kds.kek.jp/getFile.py/access?contribId=18&sessionId=40&resId=0&materialId=slides&confId=15455[2]

4

2) Emulsion experiment [3]

Emulsion stacks are exposed by 2.3 and 2.5 GeV/c2 K-

3LH → 3He + p- (3 in-flight and 1 at rest decays)

Observed the life-time for 3LH : 0.9+2.2

-0.4 ×10-10 s

If life-time of 3LH is shorter than free , L BL of 3

LH may be reconsidered

Life-time of 3LH(<=180 ps) should be nearly equal to that of ( 263L ps) because BL is very small

Expect to confirm information of life-time with many statistic events in nuclear emulsion

[3] R. J. Prem and P. H. Steinberg , Physical Rev. vol136,number 6 B, Dec,1964

5

Nuclear Emulsion

Emulsion are composed of 8 materials and AgBr is the large amount of them

AgBr crystal

Microscopic image

The best detector for the short-life nuclei

The charged particle loss their energy according to the ionization along their ranges traveled in emulsion

Ranges can be transformed into Kinetic energy with

When charged particle passed through emulsion

After photographic developing

Latent image

6

Searching 3LH hypernucleus events in nuclear emulsion

3LH → 3He + p- (two body decay)

3LH → 2H +1

1H + p- (three body decay)

p-

3LH

3He

p-

3LH

2H

11H

p-

3LH

3He

Inflight decay At-rest decay

Schematic topology of 3LH decay in emulsion

To get many statistics of 3LH events (more than 5×102 events)

Detect events in emulsion plates of KEK-PS E373 experiment by Overall-scanning method

presented by Dr. J. Yoshida

7

Emulsion plate

Eye check events in 3 dimensions under microscope

X

y

z

Output images from overall-scanning

Automatic scanning

Event detection

8

Event categorization

Single candidate events Uranium decayed series

Beam interaction Thorium decayed seriesHammer track And so on

By seeing topology of events, the event types are classified as

Among single hypernucleus events, mesonic decayed events for 3LH

have to choice

9

Estimation of mesonic decay

Overall-scanning detect full volume of emulsion plates

Even the test scan of overall-scanning, we found the two mesonic decay events for candidates of L3H from (3cm×3cm) scan area

#1 #2

#3#4

#1

#3 #2

#4

We estimate mesonic decay events nearly 100 in one plate (25×24.5)cm2

Beam

Beam

10

Construction of invariant mass

range, angle theta and phi of daughter particles

Kinetic energies &

momentum

Invariance Mass

Our measurement result will be checked with consistence of other experiments

From the measured invariant mass, range , momentum, BL and life-time are estimated

11

Summary

Reviewed experiments for life-time of L3H, their estimation interval is large

To provide and confirm precisely BL and life-time of L3H, high statistics of

L3H candidates are searched

The emulsion plates of KEK-PS E373 experiment are detected with overall-scanning method

We estimate the mesonic decay events nearly 100 for the candidates of L3H in one emulsion plate

The precise information of Life time and BL of L3H will be estimated from the invariant mass constructed with emulsion data

12

Measuring mass of single-L hypernucleus

• The mass of single hypernucleus can be constructed from momentum and energy of daughter fragments

Kinetic energy of daughter particles

Ranges of daughter particles in nuclear emulsion with range-

energy relation

Momentum of daughter particles

Image of single

candidate event

Before analysis, the range and energy should be calibrated

13

Range-Energy Relation depend on density and shrinkage factor of nuclear emulsion plate

Calibrated by using monochromic a particles

Range-energy Calibration

shrinkage factor (S) =thickness of emulsion plate at beam exposure

thickness of emulsion plate at measurement

14

Dz2 ( m

m2 )

Dx2+Dy2(mm2)

2222 SzyxR DDD

Range distribution of a particles decayed from 212Po

222222 /))(/1( SRyxSz DDD

Compare with linear equation,

Range of a particles as;

cmxy 2/1 Sm 22 / SRc

Where, S = shrinkage factor

S = 2.29 ± 0.01

R = 48.94±0.30mm

By using the well known energy 8.484MeV

Density of emulsion = 3.75 ± 0.14 g/cm3

Range→ Kinetic energy → momentum

15

y

z

x

By fitting of the data points in linear on x-y plane and x-z as y = a x + b z = c x + dparameters a, b, c, d are obtained

The parameters are fitted by c2 liner fitting method

)(2)()( 01

02

0dEzDV t

By the use of constraints Hi= yi-axi-b

Hi= zi-cxi-d

Minimizing with respect to a, l and z

1)( EVEV Dt

E

0t

EEVz

Where;

d

c

b

a

z

zi

yi

xi

c

a21tan

c

a21arctan

atan

aarctan

Measuring angles q and f of tracks

Momentum, q, f of tracks are known15

16

BL of single-L hypernucleus

From measured mass of sinlge-L hypernucleus, BL will be obtained as

XMΛMXMB AΛ

1AZΛ

The Life time (T) can be measured from the range (R) and momentum(P) as

T

R

p

M

Life-time of single-L hypernucleus

17

Introduction

Aim is to measure BL and life-time of light single-L hypernuclei precisely with nuclear emulsion

So far the error of BL of light single- L hypernucleus such as L3H is large since the number of events is a few

Overall-scanning method detect full volume of emulsion plate (Already presented by Dr. J. Yoshida)

To search many number of single-L hypernuclear events, emulsion plates of KEK-PS E373 experiment are detected with overall-scanning method

Recently, counter experiment suggested the life-time of L3H is smaller than that of L hyperon

Life-time of L3H will be confirmed with nuclear emulsion experiment

18

Summary

The emulsion plates of KEK-PS E373 experiment are detected with overall-scanning method to search many number of single hyper events

The mass of singe nucleus is measured from the kinetic energy and momentum of daughter fragments

Range and energy is calibrated with the tracks of alpha particle decayed in thorium and uranium series.

BL and life-time will be measured from the constructed mass , range and momentum of single hypernucleus in nuclear emulsion

19